1. Field of the Invention
The present invention relates to a method and apparatus for drawing a mouth-neck portion of a bottle composed of a saturated polyester resin or a precursor intermediate product thereof.
2. Description of the Prior Art
Saturated polyester resins are excellent in the physical properties and durability. However, in order to manifest these excellent physical properties and durability in saturated polyester resins, it is indispensable that these saturated polyester resins should be drawn.
Therefore, according to conventional techniques, bottles of saturated polyester resins are prepared by forming a primary intermediate molded article having an effective cylindrical shape by injection molding, blow-molding this primary intermediate molded article into a bottle and drawing the so formed bottle.
According to the conventional techniques, the bottles are subjected to drawing at the blow-molding step, and as is well known, at the blow-molding step, the mouth-neck portion of the bottle is held on a mold for blow molding. Therefore, the mouth-neck portion of the bottle is not substantially subjected to the drawing operation.
Accordingly, the undrawn mouth-neck portion is inferior to the drawn barrel portion of the bottle in the physical properties and durability, and the bottle is not completely satisfactory in the physical properties and durability.
For example, when a high concentration is stored in this conventional bottle, no trouble is caused in the barrel portion but the mouth-neck portion is whitened and becomes mechanically brittle since the alcohol permeates in the mouth-neck portion. Furthermore, a great number of fine cracks are formed in the mouth-neck portion and the sealing effect is drastically reduced.